Green’s Dictionary of Slang

1. to sleep.

1819		P. Egan Key to the Picture of the Fancy going to a Fight 16: [T]he Lower Orders of Society [...] roost well without any coaxing of laudanum to close their shutters.
1899		‘Pot’ & ‘Swears’ Scarlet City 225: The sun was shining gallantly when we adjourned to roost.
1900		Bulletin (Sydney) 6 Oct. 12/3: When you visit a house, and are shown over it, you often wonder where the ‘old man’ sleeps, for you only ever hear of ‘Mrs. Smith’s’ or ‘Mrs. Beecham’s’ room. [...] [T]he chief butler announced ‘Lady Gormanston’s room, gentlemen.’ Whereupon a country farmer-member sidled up to the chief flunkey, and, said he, ‘Say, boss, where did the old boy roost?’.
1945		T. Harris Escape from the Legion 53: ‘Some nerve to put four of us in these cells!’ [...] ‘And where do you think the new chap is going to roost?’ .

2. to sit down.

1832		Egan Bk of Sports 24: Even Tom Cox [...] could not find roosting-places for his numerous customers.
1885		Bulletin (Sydney) 24 Jan. 7/1: The fair typo., however, does not let her terrible genealogy lift her out of her boots, but she roosts in front of her case 12 hours a day, and, when her toil is done, fills herself up to the ears in nectar and sucks at a black clay, after the fashion of the gay caravan to which she now belongs.
1899–1900		(?) H. Lawson ‘New Year’s Night’ in Roderick (1972) 339: It’s too d[amne]d hot to roost indoors.
1923		P. MacGill Moleskin Joe 98: ‘If you’ll just sit down it will be much easier.’ ‘I’m roostin’,’ said Moleskin, floppin’ on a form.
1931		D. Runyon ‘Hold ’Em, Yale!’ Runyon on Broadway (1954) 153: The Harvards will not [...] pull down the goal posts with a lady roosting on them.
1941		P. Gallico Snow Goose 42: [British speaker] We was roostin’ on the beach between Dunkirk an’ Lapanny, like a lot o’ bloomin’ pigeons on Victoria Hembankment, waitin’ for Jerry to pot us. ‘E potted us good too.
1948		J. Evans Halo For Satan (1949) 146: Certainly I got a look at it. You think I’d be roosting here if I didn’t.
1958		H. Ellison Web of the City (1983) 33: The steady squares were out on the door-stoops [...] All the time just roosting on their butts.